Supplying enhanced computer user&#39;s context data

ABSTRACT

Techniques are described for providing information about a current state that is modeled with multiple state attributes. In some situations, the providing of information includes receiving from first and second sources indications of ability to supply values for, respectively, an indicated one of the state attributes and another of the state attributes. In such situations, after receiving an indication of the indicated attribute from a first client, the providing of information further includes determining that the first source is available to supply a value for the indicated attribute, obtaining from the first source an indication of the value and information describing the indicated value, determining based at least in part on the descriptive information whether the indicated value is appropriate to be supplied to the client, and supplying the indicated value to the client when it is determined that the indicated value is appropriate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/724,893 now U.S. Pat. No. 6,812,937 filed Nov. 28, 2000, which ishereby incorporated by reference in its entirety. U.S. patentapplication Ser. No. 09/724,893 is a continuation-in-part of U.S. patentapplication No. Ser. 09/216,193, entitled “METHOD AND SYSTEM FORCONTROLLING PRESENTATION OF INFORMATION TO A USER BASED ON THE USER'SCONDITION” and filed Dec. 18, 1998 now U.S. Pat. No. 6,466,232, and acontinuation-in-part of U.S. patent application Ser. No. 09/464,659,entitled “STORING AND RECALLING INFORMATION TO AUGMENT HUMAN MEMORIES”and filed Dec. 15, 1999 now U.S. Pat. No. 6,513,046. Both of theseapplications are also hereby incorporated by reference in theirentirety.

This application and U.S. patent application Ser. No. 09/724,893 alsoclaims the benefit of provisional U.S. Patent Application No.60/194,001, entitled “SUPPLYING ENHANCED COMPUTER USER'S CONTEXT DATA”and filed Apr. 2, 2000, and of provisional U.S. Patent Application No.60/193,999, entitled “OBTAINING AND USING CONTEXTUAL DATA FOR SELECTEDTASKS OR SCENARIOS, SUCH AS FOR A WEARABLE PERSONAL COMPUTER” and filedApr. 2, 2000. These applications are both hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The following disclosure relates generally to computer-based modeling ofinformation, and more particularly to modeling and exchanging contextdata, such as for a wearable personal computer.

BACKGROUND

Computer systems increasingly have access to a profusion of inputinformation. For example, a computer may be able to receive instructionsand other input from a user via a variety of input devices, such as akeyboard, various pointing devices, or an audio microphone. A computermay also be able to receive information about its surroundings using avariety of sensors, such as temperature sensors. In addition, computerscan also receive information and communicate with other devices usingvarious types of network connections and communication schemes (e.g.,wire-based, infrared or radio communication).

Wearable personal computers (or “wearables”) can have even greateraccess to current input information. Wearables are devices that commonlyserve as electronic companions and intelligent assistants to theirusers, and are typically strapped to their users' bodies or carried bytheir user in a holster. Like other computers, wearables may have accessto a wide variety of input devices. Moreover, in addition to moreconventional input devices, a wearable may have a variety of other inputdevices such as chording keyboards or a digitizer tablet. Similarly, awearable computer may have access to a wide variety of sensors, such asbarometric pressure sensors, global positioning system devices, or aheart rate monitor for determining the heart rate of its user. Wearablesalso may have access to a wide variety of non-conventional outputdevices, such as display eyeglasses and tactile output devices.

Many applications executing on computers utilize data received by thecomputer from sensors or other input sources. For example, a positionmapping application for a wearable computer may utilize data receivedfrom a global positioning system device in order to plot its user'sphysical location and to determine whether that position is within aspecified region. In this example, the global positioning system deviceproduces data that is consumed by the position mapping application.

In conventional wearable computer systems, the position mappingapplication would be designed to interact directly with the globalpositioning system device sensor to obtain the needed data. For example,the application may be required to instruct the device to obtainposition information, retrieve the information obtained by the device,convert it to conventional latitude and longitude representation, anddetermine whether the represented location is within the special region.

The need for such direct interaction between applications and sensors inorder to obtain and process data has several significant disadvantages.First, developing an application to interact directly with a particularsensor can introduce sensor-specific dependencies into the application.Accordingly, the application may need to be subsequently modified to beable to interact successfully with alternatives to that sensor providedby other manufacturers, or even to interact successfully with futureversions of the same sensor. Alternately, the sensor could be developedto explicitly support a particular type of application (e.g., via adevice driver provided with the sensor), which would analogouslyintroduce application-specific dependencies into the sensor.

Second, direct interaction between the application and the sensor cangive rise to conflicts between multiple applications that consume thesame data. For example, if the position mapping application wasexecuting on the same wearable computer as a second application fordetermining the user's distance from home, and the second applicationalso used the global positioning system device, the two applications'interactions with the device could interfere with one another.

Third, direct interaction between the application and the sensor cangive rise to conflicts between multiple sensors that produce the samedata. For example, if the position mapping application was executing ona wearable computer that had access to both the global positioningsystem device and an indoor positioning system, the application mightwell have trouble determining which device to use to determine theuser's current position, and/or have trouble reconciling data producedby both devices.

Fourth, rather than an application having to directly process observabledata from the sensors and derive more abstract information itself, itwould be advantageous for the application to be able to rely on aseparate programmatic entity that derives such abstract information andprovides it to the application. For example, it would be more convenientfor the position mapping application to be able rely on a separateprogrammatic entity that determines the user's location, and to then usethat information to determine whether the user is in a special region.

Accordingly, a facility for exchanging information between sensors andapplications in a wearable computer system would have significantutility.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the characterization moduleexecuting on a general-purpose body-mounted wearable computer.

FIG. 2 is a block diagram illustrating an embodiment of thecharacterization module executing on an exemplary computer system.

FIG. 3 is a data flow diagram showing a sample exchange of attributesperformed by the characterization module.

FIG. 4 is a data structure diagram showing an example context servertable used to maintain a portion of the state of the characterizationmodule.

FIG. 5 is a data structure diagram showing an example attribute instancetable used to maintain a portion of the state of the characterizationmodule.

FIG. 6 is a data structure diagram showing an example context clienttable used to maintain a portion of the state of the characterizationmodule.

FIG. 7 is a data structure diagram showing updated contents of theattribute instance table.

FIG. 8 is a flow diagram of an embodiment of the GetAttribute function.

FIG. 9 is a data structure diagram showing updated contents of theattribute instance table.

FIG. 10 is a data structure diagram showing an example condition tablethat contains a portion of the state of the characterization module.

FIG. 11 is a data structure diagram showing an example condition monitortable that maintains a portion of the state of the characterizationmodule.

FIG. 12 is a data structure diagram showing updated contents of thecondition monitor table.

FIG. 13 is a data flow diagram showing the operation of the facilitywithout a characterization module.

FIG. 14 is a data structure diagram showing an example attribute requesttable used to maintain a portion of the state of the characterizationmodule.

FIG. 15 illustrates an example of a plain-language, hierarchical,taxonometric attribute nomenclature.

FIG. 16 illustrates an example of an alternate hierarchical taxonomyrelated to context.

FIG. 17 is a flow diagram of an embodiment of the CharacterizationModule routine.

FIG. 18 is a flow diagram of an embodiment of the NotificationProcessing subroutine.

FIG. 19 is a flow diagram of an embodiment of the Dynamically SpecifyAvailable Clients, Servers, and Attributes subroutine.

FIG. 20 is a flow diagram of an embodiment of the Process DistributedCharacterization Module Message subroutine.

FIG. 21 is a flow diagram of an embodiment of the Process AttributeValue Or Value Request Message subroutine.

FIG. 22 is a flow diagram of an embodiment of the Process ReceivedAttribute Value subroutine.

FIG. 23 is a flow diagram of an embodiment of the Process AdditionalInformation About Received Value subroutine.

FIG. 24 is a flow diagram of an embodiment of the Mediate AvailableValues subroutine.

FIG. 25 is a flow diagram of an embodiment of the Pull Attribute ValueFrom Server subroutine.

FIG. 26 is a flow diagram of an embodiment of the Push Attribute ValueTo Client subroutine.

FIG. 27 is a flow diagram of an embodiment of the Context Clientroutine.

FIG. 28 is a flow diagram of an embodiment of the Context Serverroutine.

DETAILED DESCRIPTION

A software facility is described below that exchanges informationbetween sources of context data and consumers of context data. Inparticular, in a preferred embodiment, a characterization moduleoperating in a wearable computer system receives context informationfrom one or more context servers (or “suppliers”), and provides thatinformation to one or more context clients (or “consumers”). Thiscontext information represents a particular context (or “state” or“condition”) of the wearable, the user of the wearable, the surroundingphysical environment and/or the available electronic data environment(or “cyber-environment”). In some embodiments the context is represented(or “modeled”) with a variety of attributes (or “variables”) eachmodeling a single aspect of the context. By facilitating the exchange ofcontext information, the facility reduces dependencies of context clientapplications on specific sensors and other input sources, resolvesconflicts between context client applications that consume the samecontext data, resolves conflicts between multiple sensors or other inputsources that produce the same data, and isolates the generation ofderived attributes from context client applications.

A context is modeled or represented with multiple attributes that eachcorrespond to a specific element of the context (e.g., ambienttemperature, location or a current user activity), and the value of anattribute represents a specific measure of that element. Thus, forexample, for an attribute that represents the temperature of thesurrounding air, an 80° Fahrenheit value represents a specificmeasurement of that temperature. Each attribute preferably has thefollowing properties: a name, a value, an uncertainty level, units, anda timestamp. Thus, for example, the name of the air temperatureattribute may be “ambient-temperature,” its units may be degreesFahrenheit, and its value at a particular time may by 80. Associatedwith the current value may be a timestamp of Feb. 27, 1999 13:07 PSTthat indicates when the value was generated, and an uncertainty level of+/−1 degrees.

Context servers supply values for attributes by receiving and processinginput information from sensors or other sources. Attribute valuesprovided by a context server may either be “measured” (or “observed”) inthat they are directly received from an input source, or may instead be“derived” in that they are the result of performing processing on one ormore measured attribute values. Indeed, a derived attribute value may beproduced by performing additional processing on one or more otherderived attribute values. Context attributes (or “condition variables”)are discussed in greater detail in both U.S. patent application Ser. No.09/216,193, filed Dec. 18, 1998 and entitled “METHOD AND SYSTEM FORCONTROLLING PRESENTATION OF INFORMATION TO A USER BASED ON THE USER'SCONDITION”, and provisional U.S. Patent Application No. 60/193,999,filed Apr. 2, 2000 and entitled “OBTAINING AND USING CONTEXTUAL DATA FORSELECTED TASKS OR SCENARIOS, SUCH AS FOR A WEARABLE PERSONAL COMPUTER,”which are both hereby incorporated by reference.

When the characterization module obtains an attribute value from acontext server, it caches the value for use when responding to futurerequests from context clients for a value of the attribute. Thus, whenthe characterization module receives a request from a context client forthe value of an attribute, the characterization module determineswhether it has a cached value for the attribute and, if so, whether thevalue is sufficiently accurate (e.g., the value does not have too highof an uncertainty) and/or sufficiently recent (e.g., the value is nottoo old). If the value is not sufficiently accurate or recent, thecharacterization module requests and receives an updated value for theattribute from the context server that supplied the value. When thecharacterization module has a sufficiently accurate and recent value, itsupplies the value to the context client. The determination of whether avalue is sufficiently accurate and recent can be made in a variety ofways, such as by using thresholds for recency or uncertainty that can bespecified by the context client during the request, by a context serverfor all values of an attribute or for a specific attribute value, or bythe characterization module.

In some embodiments, two or more different context servers may supply tothe characterization module their own distinct values for a singleattribute. For example, a first context server can supply a value for auser.location attribute based on data received from a global positioningsystem device, while a second context server can supply a value for theuser.location attribute based on data received from an indoorpositioning device. Alternately, the first and second context serverscould use the same input information when determining the value for asingle attribute, but could use different methods to perform thedetermining and could thus arrive at different values. When multiplecontent servers supply values for the same attribute, each of thecontext servers is said to supply values for a separate “instance” ofthe attribute. The characterization module preferably provides a varietyof different approaches, called “mediators,” for determining whatattribute value to provide when a context client requests a value for anattribute that has more than one instance.

For attributes with multiple instances, the characterization moduleperforms similar processing to that described above. In particular, thecharacterization module can maintain a unique cached value for eachattribute instance. If the characterization module receives a requestfor a value of a particular attribute instance, the request is handledas discussed above. If the characterization module instead receives aattribute value request for an attribute with multiple instances and therequest does not specify a particular instance, the characterizationmodule checks the accuracy of each cached attribute instance andrequests an updated value for any instance with a value that is notsufficiently accurate. If multiple sufficiently accurate values areavailable, the characterization module produces a mediated value that isreturned to the context client. The mediator to be used for themediation can be selected in a variety of ways, such as being a defaultmediator of the characterization module, being requested by a contextclient, being specified by one or more of the context servers, or beingchosen by the characterization module.

The manner in which data (e.g., sensor data and attribute values) flowsto and from the characterization module can vary. In some embodiments, acontext client may receive an attribute value only after an explicitrequest, while in other embodiments a context client may be forwardedattribute values without a request (e.g., if the client had previouslyexpressed an interest in receiving values for the attribute and a valuehas just become available). Similarly, in some embodiments contextservers may supply attribute values only when requested, while in otherembodiments the context servers may supply attribute values without arequest (e.g., if sensor input information is received from which a newvalue is produced). Request-based processing is a type of “pull” dataflow model, and some forms of processing that occur without explicitrequests are referred to as a “push” or “event-driven” data flow model.

The manner in which the characterization module communicates with thecontext clients and context servers can also vary. In some embodiments,context servers and context clients perform various interactions withthe characterization module (e.g., supplying attribute values andrequests) by calling functions provided by the characterization module(e.g., via Component Object Module interfaces). These functions are saidto collectively comprise an “application programming interface” (or“API”) to the characterization module. In alternate embodiments, suchinteractions can be performed using other mechanisms, such as passingmessages or objects. Those skilled in the art will appreciate that anAPI can be created to support a pull data model, a push data model, or ahybrid system including both push and pull functionality.

As one example of an API, each executing context server may registerwith the characterization module by calling a RegisterContextServerfunction and supplying parameters to identify itself. If a particularcontext server is not executing, a context client that desires a valueof an attribute or attribute instance supplied by the context server maycause the context server to be launched by using a LaunchContextServerfunction. After registration, a context server may indicate an abilityto supply values for an attribute to the characterization module byusing a CreateAttributeInstance function. A particular context servercan provide values for a number of different attributes by calling theCreateAttributeInstance function multiple times. In order to consumevalues of an attribute, a context client may call aRegisterContextClient function in order to identify itself and one ormore attributes whose values it seeks to consume. To assist in selectingone or more attributes, a context client may also call aEnumerateAttributes function to obtain a list of the attributesavailable from the characterization module. In order to actuallyretrieve an attribute value, a context client may call a GetAttributefunction and use parameters to identify the attribute and any attributeprocessing that should be applied, such as a specific mediator to beused if values are available for multiple instances of the attribute.For attributes that have multiple instances in the characterizationmodule, a context client may also call a GetAllAttributeInstancesfunction to obtain a value for each instance of the attribute. To forcea particular context server to reevaluate all of its attributeinstances, a context client may call a CompleteContextServerEvaluationfunction. Also, to retrieve values for attributes that model aspects ofthe configuration of the characterization module, a context client orother program may call a GetCharacterizationModuleAttribute function. Acontext client that consumes a particular attribute value may alsocreate a condition in the characterization module (not to be confusedwith the current modeled condition of the user or the environment thatis represented by various attribute values) for testing that attributeby calling a CreateCondition function. Once a context client has createda condition, it can evaluate the condition by calling anEvaluateCondition function using parameters to identify the condition,and may also proceed to create a condition monitor that monitors thecondition and notifies the context server when the condition issatisfied by calling a CreateConditionMonitor function. To suspendoperation of a created condition monitor, a context server may call aStopConditionMonitor function, and to resume its operation, may call aStartConditionMonitor function. The context server may remove acondition monitor that it created by calling a RemoveConditionMonitorfunction and, correspondingly, may remove a condition that it created bycalling a RemoveCondition function. A context client may unregister withthe characterization module by calling an UnregisterContextClientfunction. A context server may similarly remove attribute instances thatit has registered by calling a RemoveAttributeInstance function. Beforeit does, however, it may first call a CheckAttributeInstanceDependenciesfunction to determine whether any context clients currently depend uponthat attribute instance. A context server may unregister with thecharacterization module by calling an UnregisterContextServer function.A set of API functions are discussed in greater detail in both U.S.patent application Ser. No. 09/541,328, filed Apr. 2, 2000 and entitled“INTERFACE FOR EXCHANGING CONTEXT DATA,” and provisional U.S. PatentApplication No. 60/194,123, filed Apr. 2, 2000 and entitled “SUPPLYINGAND CONSUMING USER CONTEXT DATA,” which are both hereby incorporated byreference.

In some embodiments, it may also be useful to store attribute valueinformation in a more permanent fashion than a temporary cache. Forexample, it may be useful for the characterization module to keep a logof all attribute values received and sent, or of all interactions withcontext clients and context servers. Alternately, it may be useful torecord the current values of some or all of the attributes and attributeinstances at the same time, such as to capture a complete model of thecurrent context. Storing attribute value information is discussed ingreater detail in both U.S. patent application Ser. No. 09/464,659,filed Dec. 15, 1999 and entitled “STORING AND RECALLING INFORMATION TOAUGMENT HUMAN MEMORIES”, and U.S. patent application Ser. No.09/541,326, filed Apr. 2, 2000 and entitled “LOGGING AND ANALYZINGCOMPUTER USER'S DATA,” which are both hereby incorporated by reference.Other uses of attribute value information are described in provisionalU.S. Patent Application No. 60/194,000, filed Apr. 2, 2000 and entitled“SOLICITING PRODUCT INFORMATION BASED ON THE USER'S CONTEXT,” inprovisional U.S. Patent Application No. 60/194,002, filed Apr. 2, 2000and entitled “AUTOMATED SELECTION OF UNSOLICITED INFORMATION BASED ON AUSER'S CONTEXT,” and in provisional U.S. Patent Application No.60/194,758, filed April 2, 2000 and entitled “CREATING PORTALS BASED ONTHE USER'S CONTEXT,” each of which are hereby incorporated by reference.

FIG. 1 illustrates an embodiment of the characterization module whichexecutes on a general-purpose body-mounted wearable computer 120 worn byuser 110. Many wearable computers are designed to act as constantcompanions and intelligent assistants to a user, and are often strappedto a user's body or mounted in a holster. The computer system may alsobe incorporated in the user's clothing, be implanted in the user, followthe user, or otherwise remain in the user's presence. In one preferredembodiment the user is human, but in additional preferred embodiments,the user may be an animal, a robot, a car, a bus, or another entitywhose context is to be modeled. Indeed, the computer system may have noidentifiable user, but rather operate as an independent probe, modelingand/or reporting on the context in an arbitrary location.

The wearable computer 120 has a variety of user-worn user input devicesincluding a microphone 124, a hand-held flat panel display 130 withcharacter recognition capabilities, and various other user input devices122. Similarly, the computer has a variety of user-worn output devicesthat include the hand-held flat panel display, an earpiece speaker 132,an eyeglass-mounted display 134, and a tactile display 136. In additionto the various user-worn user input devices, the computer can alsoreceive information from various user sensor input devices 116 and fromenvironment sensor input devices 128, including video camera 121. Thecharacterization module can receive and process the various inputinformation received by the computer, either directly or from contextservers that process the input information and generate attributevalues, and can supply the received information to context clients ordirectly to the user by presenting the information on the various outputdevices accessible to the computer.

In the current environment, computer 120 is accessible to a computer 150(e.g., by being in line-of-sight wireless proximity or by beingreachable via a long-distance communication device such as a cellularphone) which also has a variety of input and output devices. In theillustrated embodiment the computer 150 is non-portable, although thebody-mounted computer of the user can similarly communicate with avariety of other types of computers, including body-mounted computers ofother users. The devices from which the non-portable computer candirectly receive information include various user input devices 152 andvarious user sensor input devices 156. The non-portable computer canoutput information directly to a display 160, a speaker 162, anolfactory device 164, and a printer 166. In the illustrated embodiment,the body-mounted computer can communicate with the non-portable computervia a wireless transmission medium. In this manner, the characterizationmodule can receive information from the user input devices 152 and theuser sensor devices 156 after the information has been transmitted tothe non-portable computer and then to the body-mounted computer.Alternately, the body-mounted computer may be able to directlycommunicate with the user input devices 152 and the user sensor devices156, as well as with other various remote environment sensor inputdevices 158, without the intervention of the non-portable computer 150.Similarly, the body-mounted computer may be able to supply outputinformation to the display 160, the speaker 162, the olfactory device164, and the printer 166, either directly or via the non-portablecomputer, and directly to the telephone 168. As the user moves out ofrange of the remote input and output devices, attribute values of thecharacterization module can be updated to reflect that the remotedevices are not currently available.

Information that is received from the various input devices allows thecharacterization module or an application such as a context server (notshown) executing on the computer 120 to monitor the user and theenvironment, and to maintain a model (not shown) of the current context.In some embodiments, the model may be represented in a single location(e.g., the current cached values of all of the context attributes andattribute instances), while in other embodiments the model may bedistributed. Such a model can be used by various applications, such ascontext clients, for a variety of purposes. A model of the currentcontext can include a variety of context attributes that representinformation about the user, the computer, and the user's environment atvarying levels of abstraction. For example, information about the userat a low level of abstraction can include raw physiological data (e.g.,heart rate and EKG) and geographic information (e.g., location andspeed), while higher levels of abstraction may attempt to characterizeor predict the user's physical activity (e.g., jogging or talking on aphone), emotional state (e.g., angry or puzzled), desired outputbehavior for different types of information (e.g., to present privatefamily information so that it is perceivable only to myself and myfamily members), and cognitive load (i.e., the amount of attentionrequired for the user's current activities). Background informationwhich changes rarely or not at all can also be included, such as theuser's age, gender and visual acuity. The model can similarly holdenvironment information at a low level of abstraction, such as airtemperature or raw data from a motion sensor, or at higher levels ofabstraction, such as the number and identities of nearby people,objects, user mood, and locations. The model of the current context caninclude information added explicitly from other sources (e.g.,application programs), as well as user-specified or system-learneddefaults and preference information.

Those skilled in the art will appreciate that computer systems 120 and150, as well as their various input and output devices, are merelyillustrative and are not intended to limit the scope of the presentinvention. The computer systems may contain additional components or maylack some illustrated components. For example, the characterizationmodule could be implemented on the non-portable computer, with thebody-mounted computer replaced by a thin computer client such as atransmitter/receiver for relaying information between the body-mountedinput and output devices and the non-portable computer. Alternately, theuser may not wear any devices or computers.

In addition, the body-mounted computer may be connected to one or morenetworks of other devices through wired or wireless communication means(e.g., wireless RF, a cellular phone or modem, infrared, physical cable,a docking station, etc.), either with or without support from othercomputers such as the computer 150. For example, the body-mountedcomputer of a user can make use of output devices in a smart room, suchas a television and stereo when the user is at home, if the body-mountedcomputer is able to transmit information to those devices via a wirelessmedium or if a cabled or docking mechanism is available. Alternately,kiosks or other information devices can be installed at variouslocations (e.g., in airports or at tourist spots) to transmit relevantinformation to body-mounted computers within the range of theinformation device. Those skilled in the art will also appreciate thatspecialized versions of the body-mounted computer, characterizationmodule, context clients and/or context servers can be created for avariety of purposes.

FIG. 2 illustrates an exemplary computer system 200 on which anembodiment of the characterization module is executing. The computerincludes a memory 230, a CPU 210, a persistent storage device 250 suchas a hard drive, and input/output devices including a microphone 222, avideo camera 223, a computer-readable media drive 224 (e.g., a CD-ROMdrive), a visual display 225, a speaker 226, and other devices 228. Thememory preferably includes the characterization module 231, as well asinformation reflecting the current state of the characterization module(characterization module state) 232. The memory further containssoftware modules 233, 234, and 237 that consume attribute values and aretherefore context clients, and software modules 235, 236, and 237 whichprovide attribute values and are therefore context servers. While items231-237 are preferably stored in memory while being used, those skilledin the art will appreciate that these items, or portions of them, can betransferred between memory and the persistent storage device forpurposes of memory management and data integrity. Alternately, in otherembodiments some or all of the software modules may execute in memory onanother device, and communicate with the characterization module viainter-computer communication.

In addition, in some embodiments a pre-defined set of attributes areavailable for use by context servers and context clients. This allows acommon meaning to be shared between context clients and context serversas to those attributes and their values, and can also allow a contextclient to request a pre-defined attribute without having to determinewhether the attribute has been created by a context server supplyingvalues for the attribute. In one embodiment a plain-language,hierarchical, taxonometric attribute nomenclature is used to nameattributes, such as the example attribute nomenclature illustrated inFIG. 15. The names within the nomenclature are preferably specific sothat there is no ambiguity as to what they represent, and the ability toextend the nomenclature by adding new attribute names that conform tothe hierarchical taxonomy of the nomenclature is preferably supported.The nomenclature preferably has attribute names relating to a variety ofaspects of the user.

For example, as is illustrated in FIG. 15, the nomenclature preferablyhas a variety of types of attribute names, including: attribute namesrelating to the user's location, such as user.location.latitude,user.location.building, and user.location.street; attribute namesrelating to the user's movement, such as user.speed and user.direction;attribute names for various user moods, such as user.mood.happiness,user.mood.anger, and user.mood.confusion; attribute names for useractivities, such as user.activity.driving, user.activity.eating, anduser.activity.sleeping; attribute names for user physiology values, suchas user.physiology.body_temperature and user.physiology.blood_pressure;attribute names for similar attributes of people other than the user,such as person.John_Smith.mood.happiness; attribute names for aspects ofthe computer system or “platform,” such as for aspects of the platform'suser interface (“UI”) capabilities (e.g.,platform.UI.oral_input_device_availability andplatform.UI.visual_output_device_availability) and central processingunit (“CPU”) (e.g., platform.cpu.load and platform.cpu.speed); attributenames for aspects of the local environment, such asenvironment.local.temperature and environment.local.ambient_noise_level;attribute names for remote environments, such asenvironment.place.chicago.time andenvironment.place.san_diego.temperature; attribute names relating to afuture context, such as those that predict or estimate a situation(e.g., environment.local.next_week.temperature); attribute namesrelating to specific applications, such as an email application (e.g.,application.mail.available, application.mail.new_messages_waiting, andapplication.mail.messages_waiting_to_be_sent); etc. In this manner, theattribute nomenclature used by the facility provides effective names forattributes relating to the user, the computer system, and theenvironment. Additional attributes are illustrated in FIG. 15, and FIG.16 illustrates an alternate hierarchical taxonomy related to context,such that various attributes could be added for each of the illustratedcategories. Those skilled in the art will appreciate that for both FIG.15 and FIG. 16, other categories and attributes could be added andexisting categories and attributes could be removed or could havealternate names.

FIG. 3 is a data flow diagram showing a sample exchange of attributesperformed by the characterization module. The diagram showscharacterization module 300, as well as five other software modules,310, 320, 330, 340, and 350. Software modules 310, 320, and 330 are saidto be context servers, in that they provide attribute values to thecharacterization module. For example, context server 330 provides valuesfor a user.in_region attribute 331. It can be seen that context serversmay provide values for more than one attribute. For example, contextserver 320 provides values for a user.location attribute 321 and anuser.elevation attribute 322. It can further be seen that values for asingle attribute may be provided by more than one context server. Forexample, context server 310 provides values for user.location attribute311, while context server 320 provides values for user.locationattribute 321. Attributes 311 and 321 will be represented by thecharacterization module as multiple instances of a single user.locationattribute. The characterization module preferably provides functionalityfor mediating between these two separate instances when the value of theuser.location attribute is requested by a context client.

Software modules 330, 340, and 350 are said to be context clientsbecause they consume attribute values. For example, context client 340consumes user.location attribute 341 values. It can be seen that certainsoftware modules may act both as a context server and as a contextclient. For example, software module 330 is both a context server and acontext client, as it provides values for the user.in_region attribute331 and consumes values for user.location attribute 332. It can also beseen that a context client can consume values for more than oneattribute. For example, context client 350 consumes values for bothuser.in_region attribute 351 and user.elevation attribute 352. Todetermine which attributes are currently available, any of the contextclients may request that the characterization module enumerate theavailable attributes. In response to such a request, thecharacterization module would enumerate the user.location attribute, theuser.elevation attribute, and the user.in_region attribute.

FIG. 4 is a data structure diagram showing an example context servertable used to maintain a portion of the state of the characterizationmodule. Each row of the table corresponds to a registered contextserver. Each row contains a context server name field 411 containing thename of the context server, a version field 412 identifying the versionof the context server, an installation date 413 identifying the date onwhich the context server was installed on the computer system, afilename 414 identifying a primary file in the file system representingthe context server, and a request handler field 415 containing areference to a request handler function on the context server that maybe called by the characterization module to send messages to the contextserver (e.g., a request evaluation of one or all of the attributesprovided by the context server). Other versions of the context servertable may lack some of the illustrated fields (e.g., the version field),or may contain additional fields (e.g., a registered attributes fieldthat contains the names of all of the attributes for which the contextserver is currently registered to supply values).

FIG. 5 is a data structure diagram showing an example attribute instancetable used to maintain a portion of the state of the characterizationmodule. The attribute instance table contains a row for each attributeor attribute instance for which a context server is currently registeredto supply values. Each of these rows contains the following fields: anattribute name field 511 containing the name of the attribute, a contextserver name field 512 identifying the context server that created theattribute instance, a value field 513 containing the value of theattribute last provided by the context server, and uncertainty field 514identifying the level of uncertainty of the value, a timestamp 515indicating the time at which the value is effective, a units field 516identifying the units for the value and the uncertainty, and anindication 517 of the number of context clients consuming values for theattribute instance. While row 501 indicates that an instance of theuser.location attribute from the gps context server has a multi-partvalue of 47° 36.73′ N and 122° 18.43′ W degrees and minutes, inalternate embodiments multi-part values may not be used, such as insteadhaving two attributes to represent this context element (e.g.,user.location.latitude and user.location.longitude). Similarly, whilefield 517 indicates the number of context clients consuming values foran attribute, in alternate embodiments this number could be dynamicallycalculated rather than being stored (e.g., by using the attributerequest table discussed below), or an identifier for each context clientcould instead be stored rather than merely a number. Other versions ofthe attribute instance table may lack some of the illustrated fields,such as the units field if all the instances of an attribute arerestricted to having the same units and if such common information aboutall the attribute instances is stored elsewhere. Alternately, someversions of the attribute instance table could include additionalinformation, such as a separate row for each attribute with multipleinstances that contains common information about all of instances, andadditional fields such as a context client field that contains the nameof each context client registered to receive values for the attribute orinstance of that row. Other versions of the attribute instance tablecould include other additional fields such as an optional specifiedcontext client field so that the context server can indicate one or morecontext clients that are able to receive values for the attribute (e.g.,a list of authorized clients).

FIG. 6 is a data structure diagram showing an example context clienttable used to maintain a portion of the state of the characterizationmodule. Each row corresponds to a registered context client, andcontains a context client name field 611 identifying the name of theregistered context client as well as a message handler field 612containing the reference to a message handler provided by the contextclient for processing messages from the characterization module. Otherversions of the context client table may lack some of the illustratedfields, or may contain additional fields (e.g., a registered attributesfield that contains the names of all of the attributes for which thecontext server is currently registered to receive values).

FIG. 7 is a data structure diagram showing updated contents of theattribute instance table illustrated in FIG. 5. It can be seen that, inresponse to registration of a location_map context client consumingvalues for the user.in_region attribute, the characterization module hasincremented the number of context clients consuming the user.in_regionattribute from 0 to 1.

FIG. 14 is a data structure diagram showing an example attribute requesttable used to maintain a portion of the state of the characterizationmodule. The attribute request table contains a row for each attributefor which a context client is currently registered to receive values.Each of these rows contains the following fields: an attribute namefield 1411 containing the name of the attribute, and a context clientname field 1412 identifying the context client that registered a requestto receive values for the attribute. Note that a context client canrequest values for an attribute without specifying a particularinstance, as in row 1401, or can instead request values for a specificattribute instance, as in row 1403. Other versions of the attributerequest table may lack some of the illustrated fields, or may containadditional fields such as an optional field to specify one or moreparticular context servers that can supply the values for the attribute(e.g., a list of authorized context servers).

FIG. 8 is a flow diagram of one embodiment of the GetAttribute function.In step 801, if the requested attribute exists, then the facilitycontinues in step 803, else the facility continues in step 802 to returnan “attribute not found” error. In step 803, if a single instance of theattribute was requested, then the facility continues in step 804, elsethe facility continues in step 811. In step 804, if the requestedinstance exists, then the facility continues in step 806, else thefacility continues in step 805 to return an “attribute instance notfound” error. In step 806, if the age criterion specified for theattribute request is satisfied, then the facility continues in step 807to return the requested attribute instance, else the facility continuesin step 808 to “freshen” the attribute instance by calling theappropriate context server's request handler to request evaluation ofthe attribute instance. In step 809, if the age criterion is satisfiedby the freshened attribute instance, then the facility continues in step807 to return the freshened attribute instance, else the facilitycontinues in step 810 to return the freshened attribute instance with an“age not satisfied” error. In step 811, where a single attributeinstance was not requested, if any registered instances of the attributesatisfy the age criterion, then the facility continues in step 816, elsethe facility continues in step 812. In step 812, the facility freshensall registered instances of the requested attribute. In step 813, if anyof the attributes freshened in step 812 satisfy the age criterion, thenthe facility continues in step 816, else the facility continues in step814. In step 814, the facility applies the requested attribute mediatorto select one instance, or otherwise derive a value from the registeredinstances. In step 815, the facility returns the instance with an “agenot satisfied” error. In step 816, where one or more instances satisfythe age criterion, if more than one instance satisfies the agecriterion, then the facility continues in step 817, else the facilitycontinues in step 807 to return the attribute instance that satisfiesthe age criterion. In step 817, the facility applies the requestedattribute mediator to select one instance from among the instances thatsatisfy the age criterion, or to otherwise derive a value from theinstances that satisfy the age criterion. After step 817, the facilitycontinues in step 807 to return the value produced by the mediator.

FIG. 9 is a data structure diagram showing updated contents of theattribute instance table illustrated in FIG. 7. It can be seen inattribute instance table 900 that, upon reevaluation by the ips contextserver of its instance of the user.elevation attribute, thecharacterization module replaced the former contents of the value,uncertainty and timestamp fields of row 903 with the values resultingfrom the reevaluation.

FIG. 10 is a data structure diagram showing an example condition tablethat contains a portion of the state of the characterization module.Condition table 1000 has a row for each condition created by a contextclient. Row 1001 contains a condition name field 1011 containing thename of the condition, a context client name 1012 identifying thecontext client that created the condition, a first logical parameterfield 1013 and a second logical parameter field 1014 identifyingattributes or conditions that are to be compared, a comparison value1015 that specifies a value to which an attribute listed in the firstlogical parameter is compared if no second logical parameter is listed,and a logical operator 1016 identifying the logical operator to beapplied in the comparison.

FIG. 11 is a data structure diagram showing an example condition monitortable that maintains a portion of the state of the characterizationmodule. Condition monitor table 1100 has a row 1101 corresponding to acondition and containing each of the following fields: a conditionmonitor name field 1111 containing the name of the condition monitor; acontext client name field 1112 containing the name of the context clientthat created the condition monitor; a condition name field 1113 thatcontains the name of the condition monitored by the condition monitor; abehavior field 1114 that indicates whether the condition monitor istriggered when the condition becomes true, when it becomes false, orwhen it changes value in either direction; a frequency field 1115showing the frequency with which the condition monitor evaluates thecondition; a condition last evaluated field 1116 showing the time atwhich the condition monitor last evaluated the condition; a triggerhandler reference 1117 that identifies a trigger handler function of thecontext client that is to be called when the condition monitor istriggered; and a stop field 1118 that indicates whether the contextclient has suspended operation of the condition monitor. Such conditionmonitors can be used in a variety of ways. For example, when a contextclient is notified via the triggering of the trigger handler functionthat the value has changed, the context client can then retrieve the newvalue.

FIG. 12 is a data structure diagram showing updated contents of thecondition monitor table illustrated in FIG. 11. It can be seen from stopfield 1218 of row 1201 in condition monitor table 1200 that theregion_analysis context client has stopped, or suspended the operationof, the region boundary cross condition monitor, perhaps in response tothe observation that the user is now asleep and his or her location willremain constant.

In the foregoing, the facility is described as being implemented using acharacterization module that is called by context servers and contextclients, that caches attribute values, and that maintains statusinformation about the operation of context servers and context clients.In an alternative preferred embodiment, however, the facility operateswithout the use of such a characterization module. In this embodiment,context servers communicate directly with context clients.

FIG. 13 is a data flow diagram showing the operation of the facilitywithout a characterization module. It can be seen in FIG. 13 thatcontext servers 1310, 1320, and 1330 provide attributes directly tocontext clients 1330, 1340, and 1350. For example, it can be seen thatcontext server 1320 provides a user.elevation attribute 1322 directly tocontext client 1350. In this embodiment, the context client may itselfcache attribute values recently obtained from a context server. Further,in this embodiment, context clients may themselves interrogate contextservers for an enumeration of their attributes, and mediate betweenattribute instances provided by different context servers. For example,context client 1340 may mediate between the instance 1311 of theuser.location attribute provided by context server 1310 and the instance1321 of the user.location attribute provided by context server 1320.

In additional preferred embodiments, the facility may operate with apartial characterization module. Such a partial characterization modulemay include various combinations of the functionalities of routingcommunication between context servers and the context clients thatconsume their attribute values, caching attribute values, enumeratingavailable attributes, and providing attribute mediation.

In additional preferred embodiments, the facility may provide acharacterization module that implements a “push” information flow modelin which, each time an attribute value provided by a context serverchanges, the new value is automatically provided to context clients. Infurther preferred embodiments, the facility provides a characterizationmodule that implements a “pull” information flow model, in whichattribute values are only obtained by the characterization module fromthe context servers when they are requested by a context client. Inadditional preferred embodiments, characterization modules are providedthat support a variety of other information flow models.

FIG. 17 is a flow diagram of an embodiment of the CharacterizationModule routine 1700. The routine receives messages from context clients(CCs) and from context servers (CSes), as well as instructions fromusers, and processes the messages or instructions. In some embodiments,a CM could wait to execute code that would provide functionality untilthe functionality was requested, such as by dynamically loading code toprovide a requested mediator. The routine begins in step 1705, where thecharacterization module (CM) performs various startup operations (e.g.setting up tables in which to temporarily cache state information,retrieving previous state information, launching CSes or CCs that havepreviously registered with the CM, etc.). The routine then continues tostep 1710 to determine if the newly started CM is to take the place ofanother previously executing CM (e.g., based on a user indication whenthe new CM was started). If so, the routine continues to step 1715 toswap places with the other executing CM. One method of executing a swapthat would be transparent to the CCs and CSes interacting with the otherCM would be to request the other CM to transfer all of its current stateinformation to the new CM (e.g., registrations of CCs, CSes, andattributes, conditions and notification requests, cached values forattributes and attribute properties, etc.), to then update the other CCsand CSes so that the messages they previously sent to the other CM willnow be sent to the new CM, and to then have the other CM shutdown.

After step 1715, or if it was determined in step 1710 that another CM isnot being swapped out, the routine continues to step 1720 to receive anindication from a user or a message from a CC or CS. The routine thencontinues to step 1725 where it performs the Notification Processingsubroutine to notify any CCs or CSes about the received message or userindication if appropriate. As is explained in greater detail below, CCsand CSes can submit notification requests so that they will be notifiedby the CM upon a particular type of occurrence. Such notificationrequests could include occurrences such as when an attribute valuechanges, when a particular CC or CS registers or unregisters, whenvalues for an attribute become available or unavailable (e.g., due toregistration or unregistration), when a CC registers or unregisters toreceive values for an attribute, when the availability of particularinput/output devices changes or other computer system features change,when a package of related themed attributes becomes available orunavailable, for changes in CM internal status (e.g., a change in thedefault mediator), etc. In addition, the notification requests can becreated based not only on explicit requests, but also after theoccurrence of a particular type of event (e.g., if a CC requests a valuefor an attribute for which no CSes are currently supplying values, anotification request could be automatically created to alert the CC if aCS later registers to supply values for the attribute). Moreover,additional information about the notification requests can be supplied(e.g., a number of times that the submitter wants to receivenotifications for the request, or an expiration date after which thenotification will be removed or become inactive).

After step 1725, the routine continues to step 1730 to determine if aregistration or unregistration message was received. If so, the routinecontinues to step 1735 to execute the Dynamically Specify AvailableClients, Servers, and Attributes subroutine. Thus, CCs and CSes canregister and unregister dynamically as they become available orunavailable, and can similarly modify the status of the attributes thatthey have registered with the CM. If a registration or unregistrationmessage was not received in step 1730, the routine instead continues tostep 1740 to determine if an attribute value or a request for anattribute value has been received from a CC or CS. If so, the routinecontinues to step 1745 to execute the Process Attribute Value Or ValueRequest Message subroutine. This subroutine will satisfy requests forattribute values if possible (e.g., by supplying a cached value orrequesting one or more CSes to supply the value) and will return therequested value or an error message. Similarly, when attribute valuesare pushed to the CM from a CS, the CM will send the values ifappropriate to CCs that have registered an interest in receiving valuesfor the attribute.

If an attribute value or an attribute value request has not beenreceived from a CC or CS in step 1740, the routine instead continues tostep 1750 to determine if a request has been received to establish ormodify a condition that monitors attribute values or other conditions,or to establish or modify a condition monitor. If so, the routinecontinues to step 1755 to process the request. As described previously,conditions and condition monitors can be created, removed, and havetheir operation suspended (e.g., by deactivating them) or resumed (e.g.,by activating them).

If a condition-related request was not received in step 1750, theroutine continues instead to step 1760 to determine if a message relatedto one or more other executing CMs has been received, and if socontinues to step 1765 to process the message by executing the ProcessDistributed Characterization Module Message subroutine. Characterizationmodules can interact for a variety of reasons, as explained in greaterdetail below. If a message related to another CM has not been received,the routine continues instead to step 1770 to determine if a request hasbeen received to establish or modify a notification request. If so, theroutine continues to step 1775 to process the notification-relatedrequest. If a notification-related request was not received, the routinecontinues instead to step 1780 to determine if a shutdown message wasreceived (e.g., from a user). If so, the routine continues to step 1790to perform shutdown operations (e.g., notifying all registered CCs andCSes to unregister, or saving current state information), and thencontinues to step 1795 and ends. If it was instead determined that ashutdown message was not received, the routine continues to step 1782 todetermine if another supported operation has been requested. If so, theroutine continues to step 1784 to perform the other operation, and ifnot the routine continues to step 1786 to send an error message to therequester. For example, other types of operations may be a request toreceive information about all available attributes, about all attributesavailable from a particular CS, about which CCs are receiving values fora particular attribute, about properties and property values associatedwith attributes and attribute instances, to launch or shutdown a CC orCS, to receive information about an attribute taxonomy, to force a CS toreevaluate the values for all its registered attributes, to changeinternal CM information (e.g., the default mediator), to provideinformation about available packages of related themed attributes, toprovide information about available computer resources such asinput/output devices, etc. After steps 1735, 1745, 1755, 1765, 1775,1784, or 1786, the routine returns to step 1720. In other embodiments,additional types of functionality may be available or illustratedfunctionality may not be available. For example, in some embodiments anyCC or CS may need to satisfy security requirements (e.g., by verifyingtheir identity as an authorized module) before being allowed to requestinformation or functionality from the CM or to provide information tothe CM.

FIG. 18 is a flow diagram of an embodiment of the NotificationProcessing subroutine 1725. The subroutine examines the message or userindication received by the CM, determines whether any activenotification requests are satisfied by the type of message or indicationor by information contained in the message or indication, and notifiesthe submitters of any such requests when the requests are satisfied. Thesubroutine begins in step 1805 where it receives an indication of themessage or user indication received by the CM. The subroutine continuesto step 1810 to compare the received message or user indication to thenotification requests that are currently stored and active. Thesubroutine then continues to step 1815 to retrieve any additionalinformation that may be needed to determine if a notification requesthas been satisfied (e.g., a previous value for an attribute to determinehow the attribute value has changed).

The subroutine then continues to step 1820 where it determines if any ofthe notification requests have been satisfied. If not, the subroutinecontinues to step 1895 and returns, but if so the subroutine continuesto step 1825 to select the next satisfied notification request,beginning with the first. The subroutine then continues to step 1830 tosend a notification to the supplier of the request that the request wassatisfied, and can include additional information about the occurrencethat satisfied the request. The subroutine then continues step 1835 todetermine whether the notification request should be removed (e.g., ifit was defined as a one-time request, or has expired). If so, thesubroutine continues to step 1840 to remove the request, and if not thesubroutine continues to step 1845 to determine if the notificationrequest should be deactivated for the current time (e.g., so that asimilar occurrence can be monitored at a later time). After steps 1840or 1850, or if the notification request was not deactivated, thesubroutine continues to step 1855 to determine if there are moresatisfied notification requests. If so, the subroutine returns to step1825, and if not the subroutine continues to step 1895 and returns. Inaddition, the subroutine could periodically check the various storednotification requests (e.g., as a background process) to determine iftheir status should be modified (e.g., activated, deactivated, orremoved).

FIG. 19 is a flow diagram of an embodiment of the Dynamically SpecifyAvailable Clients, Servers, and Attributes subroutine 1735. Thesubroutine receives registration or unregistration requests for CCs,CSes, and/or attributes, and satisfies the requests as appropriate. Thesubroutine begins in step 1905 where it receives a registration orunregistration message. The subroutine continues to step 1910 todetermine if security authorization is needed (e.g., for any CC or CS,or for CCs and CSes executing on a different computer from the CM). Ifso, the subroutine continues to step 1915 to determine if the securityauthorization has been satisfied (e.g., by the submitter of the messagesupplying a password or a verified digital signature). It is determinedin step 1920 that the security authorization has not been satisfied, thesubroutine continues to step 1925 where it sends an error message to thesubmitter. However, if it is instead determined that the securitystandard has been satisfied, or if security authorization was not neededin step 1910, the subroutine continues to step 1930 to determine thetype of the registration or unregistration message.

If the message is determined to be related to a CC, the subroutinecontinues to step 1940 to determine if the message is to register theCC. If so, the subroutine continues to step 1941 to register the newclient if possible (e.g., if all necessary information has been providedand there is not another registered CC with the same unique identifier).If it is determined in step 1942 that an error occurred during theregistration attempt, the subroutine continues to step 1944 to send anerror message to the submitter. If no error occurred, the subroutineinstead continues to step 1946 to determine if the registration requestincludes one or more attributes of interest to be registered for theclient. If so, the subroutine continues to step 1982 to register thoseattributes. If it was instead determined in step 1940 that the receivedmessage was not to register the client, the subroutine continues to step1948 to determine if the message was to unregister the client. If so,the subroutine continues to step 1950 to unregister the client, and thencontinues to step 1952 to determine if any registered attributes remainfor the client. If so, the subroutine continues to step 1994 tounregister each of those attributes.

If it was instead determined in step 1930 that the received message wasrelated to a CS, the subroutine continues to step 1960 to determinewhether the message is to register the CS. If so, the subroutinecontinues to step 1961 to register the new server if possible. It isdetermined in step 1962 that an error occurred during the registrationattempt, the subroutine continues to step 1964 to send an error messageto the submitter. If no error occurred, however, the subroutine insteadcontinues to step 1966 to determine if the registration request includesone or more attributes to register for which the server is available tosupply values. If so, the subroutine continues to step 1982 to registerthose attributes. If it was instead determined in step 1960 that thereceived message was not to register the CS, the subroutine continues tostep 1968 to determine if the message was to unregister the server. Ifso, the subroutine continues to step 1970 to unregister the server, andthen continues to step 1972 to determine if any registered attributesremain for the server. If so, the subroutine continues to step 1994 tounregister those attributes.

If it was instead determined in step 1930 that the received message wasrelated only to one or more attributes and not to a CC or CS, thesubroutine continues to step 1980 to determine whether the message is toregister those attributes. If so, the subroutine continues to step 1982to select the next attribute, beginning with the first. The subroutinethen continues to step 1984 to determine if at least one instance of theattribute is currently registered. If so, the subroutine continues tostep 1986 to register a new instance of the attribute, and if not thesubroutine continues to step 1988 to register the first instance for theattribute. After steps 1986 or 1988, the subroutine continues to step1990 to determine if there are more attributes to be registered, and ifso returns to step 1982. If it is instead determined in step 1980 thatthe received message was not to register the attributes, the subroutinecontinues to step 1992 to determine if the message was to unregister theattributes, and if so continues to step 1994 to unregister eachattribute. After steps 1925, 1964, 1944, or 1994, or if thedetermination was made in the negative for one of steps 1946, 1948,1952, 1966, 1972, 1990, or 1992, the subroutine continues to step 1995and returns. As discussed previously, a variety of other types ofoptional information can additionally be supplied when registering CCs,CSes or attributes (e.g., various properties for the attribute).

FIG. 20 is a flow diagram of an embodiment of the Process DistributedCharacterization Module Message subroutine 1765. The subroutine receivesinformation from another CM or an instruction about another CM, andprocesses the information or instruction as appropriate. The subroutinebegins in step 2005 where it receives an indication of the receivedinformation or instruction. The subroutine then continues to step 2010to determine if security authorization is needed. If so, the subroutinecontinues to step 2012 to determine if the security has satisfied. It isdetermined at step 2014 that the security authorization has not beensatisfied, the subroutine continues to step 2016 to send an errormessage to the submitter. If it is instead determined that the securityauthorization has been satisfied or was not needed in step 2010, thesubroutine continues to step 2018 to determine whether information fromanother CM has been received.

If it is determined in step 2018 that an instruction about another CMhas been received, the subroutine continues to step 2020 to determine ifthe instruction is to register or unregister as a CC or CS of the otherCM. If so, the subroutine continues to step 2022 to rename anyattributes in the request if necessary. For example, if a current CM 1wants information about an attribute user.mood.happiness for its ownuser from another CM 2, CM 1 will have to modify the name of theattribute (e.g., to CM1.user.mood.happiness) it requests since CM 2'sattribute user.mood.happiness will refer to the user of CM 2. The samewill be true for a variety of other attributes that specify attributesrelative to the CM, but not to attributes with absolute specifications(e.g., person.ABC.mood.happiness). After step 2022, the subroutine thencontinues to step 2024 to send a request to the other CM to reflect therequest using the renamed attributes, with the other CM to perform theregistration or unregistration.

If it is instead determined in step 2020 that the instruction was not toregister or unregister, the subroutine continues to step 2026 todetermine whether the instruction is to send an attribute value or anattribute value request to the other CM. If so, the subroutine continuesto step 2028 to rename any attributes in the request if necessary, andthen continues to step 2030 to determine whether a request or anattribute value is being sent. If an attribute value is being sent, thesubroutine sends the value to the other CM in step 2032, and if arequest is being sent the subroutine sends the request in step 2034.After step 2034, the subroutine continues to step 2036 to receive therequested value or an error message, and if the value is received ratherthan an error message, the subroutine sends the received value to therequester at step 2038.

If it is instead determined in step 2026 that the received instructionis not to send an attribute value or an attribute value request, thesubroutine continues to step 2040 to determine if a group-wide attributeis to be modeled (e.g., troop morale for a group of soldiers that wouldrequire information for many or all of the soldiers). If so, thesubroutine continues to step 2042 to request attribute values from theother CMs that are needed for the modeling, and then continues to step2044 to receive the requested values or error messages. If the necessaryvalues are received to perform the modeling, in step 2046 the subroutinedetermines the value of the group-wide attribute and in step 2048 sendsthe value to the requester. In alternate embodiments, any such modelingof attributes may be performed only by CSes, with the CM merelyrequesting values from other CMs as instructed and supplying thereceived values to the appropriate CS.

If it is instead determined in step 2040 that the received instructionis not to model a group-wide attribute, the subroutine continues to step2050 to determine if the instruction is to aggregate information fromsubordinate CMs (e.g., in a hierarchical organization such as a businessor the military, the hierarchy of users can be reflected in a hierarchyof their CMs) or specialized CMs (e.g., a CM specialized to monitor auser's health and to detect health problems). If so, the subroutinecontinues to step 2052 to request the information from the other CMs asneeded, and continues to step 2054 to receive the requested informationor error messages. If the necessary information is received, in step2056 the subroutine aggregates the information, and in step 2058 sendsthe aggregated information to the requester. In alternate embodiments,any such aggregating of information may be performed only by CSes, withthe CM merely requesting information from other CMs as instructed andsupplying the received values to the appropriate CS.

If it is instead determined in step 2050 that the received instructionis not to aggregate information, the subroutine continues to step 2060to determine if the received instruction is to use the processingcapabilities of another computer or CM. If so, the subroutine continuesto step 2062 to request the other computer or CM to perform an indicatedtask. The subroutine then continues to step 2064 where it receives theresults of the task, and uses those results as if the task have beenperformed locally. If it is instead determined in step 2060 that thereceived instruction is not to use the processing abilities of anothercomputer, the subroutine continues to step 2065 to determine if thereceived instruction is to send information to a module such as a thinclient. If so, the subroutine continues to step 2067 to send theindicated information (e.g., from a CC), and if not the subroutinecontinues to step 2069 to perform another task as indicated. Forexample, other types of tasks could be to instruct another CM to swapitself out or to modify its internal state (e.g., to change a defaultmediator or to add a new mediator).

If it was instead determined at step 2018 that information from anotherCM has been received, the subroutine continues to step 2070 to determineif a registration or unregistration request has been received. If so,the subroutine continues to step 2071 to rename any attributes ifnecessary, and then continues to step 2072 to resubmit the request as iffrom a CC or a CS using the renamed attributes. If the information wasnot a registration or unregistration request, the subroutine continuesto step 2073 to determine if an attribute value or an attribute valuerequest has been received. If so, the subroutine continues to step 2074to rename the attributes if necessary, and then continues to step 2075to determine whether an attribute value or an attribute value requesthas been received. If an attribute value has been received, thesubroutine continues to step 2076 where it resubmits the value as beingfrom a CS, and if not the subroutine continues to step 2077 where itresubmits the attribute value request as being from a CC. After step2077, the subroutine continues to step 2078 where it receives therequested value or an error message, and in step 2079 sends the receivedvalue to the requesting CM if an error message was not received.

If it was instead determined in step 2073 that an attribute value orattribute value request was not received, the subroutine continues tostep 2080 to determine if the received information was an indication tomodify the internal state of the CM. If so, the subroutine continues tostep 2081 where it modifies the state as indicated. If the receivedinstruction was not to modify the internal state, the subroutinecontinues to step 2082 to determine if the request is to swap the CM outto be replaced by the other requesting CM. If so, the subroutinecontinues to step 2084 to send the current state information from the CMto the requesting CM. In addition, the CM could perform other tasks ifnecessary such as updating the currently registered CCs and CSes so thatthey now will communicate with the other CM. The subroutine thencontinues to step 2086 to wait for an indication from the other CM toexit, and after receiving the indication, submits a shutdown request instep 2088. If the received instruction was not to swap out, thesubroutine continues to step 2090 to perform the other task as indicatedif appropriate. After steps 2016, 2024, 2032, 2038, 2048, 2058, 2064,2067, 2069, 2072, 2076, 2079, 2081, 2088, or 2090, the subroutinecontinues to step 2095 and returns.

FIG. 21 is a flow diagram of an embodiment of the Process AttributeValue Or Value Request Message subroutine 1745, as illustrated in theaccompanying figure and described elsewhere. In particular, thesubroutine receives an indication of an attribute value or a request foran attribute value, and processes the value or request as appropriate(e.g., pulling values from servers when needed to satisfy requests andpushing received values to clients when appropriate). Those skilled inthe art will appreciate that in other embodiments only one of the pushand pull data flow models may be supported. The subroutine begins atstep 2105 where it receives an indication of an attribute value or arequest for an attribute value. The subroutine then continues to step2110 to determine if an attribute value or a request was received.

If a value was received, the subroutine continues to step 2120 toexecute the Process Received Attribute Value subroutine, such as tostore the value and to process additional associated informationreceived about the value. The subroutine next continues in theillustrated embodiment to push the received value or a related value toclients as appropriate. Those skilled in the art will appreciate that inother embodiments such values may merely be cached or otherwise storeduntil requested by a client. Alternately, even if received values arenot generally pushed to clients, in other embodiments such values couldbe pushed to clients in limited circumstances, such as an update to arelated value that had previously been sent to a client when the newlyreceived value is more accurate.

In the illustrated embodiment, the subroutine continues to step 2122 todetermine whether there are any previously specified requests orindications of interest related to the received value that would causethe received value or a related value to be pushed to one or moreclients. If it is determined in step 2125 that there are any suchrequests or indications, the subroutine continues to step 2130 todetermine if there are multiple attribute instance values available thatmeet the appropriate criteria (if any are specified) to satisfy therequests or indications. For example, a default or specified thresholdfor the freshness of values could be used as a criteria. If there aremultiple values, the subroutine continues to step 2132 to execute theMediate Available Values subroutine and produce a mediated value fromthe multiple available values, and in step 2134 selects the mediatedvalue produced by the subroutine. If it was instead determined in step2130 that there are not multiple attribute instance values available forthe received value, the subroutine continues to step 2136 to select thereceived value. After steps 2134 or 2136, the subroutine continues tostep 2138 to select the next request of the identified requests,beginning with the first request. The subroutine then continues to step2140 to execute the Push Selected Attribute Value To Client subroutinefor the selected request, and then continues to step 2142 to determineif there are more identified requests. If so, the subroutine returns tostep 2138 to select the next request.

If it was instead determined in step 2110 that a request for a value wasreceived, the subroutine continues to step 2150 to identify allattribute instances that match the request (e.g., that satisfy one ormore criteria for the value that are specified with the request). Thesubroutine then continues to step 2152 to determine if there are anysuch instances, and if not continues to step 2154 to send an errormessage to the requester. In the illustrated embodiment, the subroutinenext pulls current values for the identified attribute instances fromservers as appropriate. Those skilled in the art will appreciate that inother embodiments only those values that have previously been receivedand stored may be supplied to clients. Alternately, even if currentvalues are not generally pulled from servers, in other embodiments suchvalues could be pulled from servers in limited circumstances, such aswhen explicitly requested by a client.

In the illustrated embodiment, if it is determined in step 2152 that atleast one attribute instance is identified, the subroutine continues tostep 2156 to select the next such instance, beginning with the first.The subroutine in step 2158 then determines if a new value is needed forthe selected instance (e.g., the available value does not meet somespecified criteria, such as an accuracy threshold specified by therequesting client). If so, the subroutine continues to step 2160 toexecute the Pull Attribute Value From Server subroutine. The subroutinein step 2162 next waits for a value or error message response from theserver, and determines if a value is received. If a value is received,the subroutine then continues to step 2164 to execute the ProcessReceived Attribute Value subroutine. After step 2164, or if it wasdetermined in step 2158 that the instance does not need a new value orin step 2162 that a new value was received, the subroutine continues tostep 2166 to determine if there are more instances identified. If so,the subroutine returns to step 2156 to select the next such instance,and if not continues to step 2168 to determine if there are multiplevalues now available for the request that meet any relevant criteria.While all identified attribute instance values that match the requestare used in the illustrated embodiment, in other embodiments a differentor additional selection process for the values could be used. Forexample, information about the various servers that can supply theattribute instance values may be available (e.g., dynamically), and ifso only certain of the servers could be selected based on theinformation with only the values from those servers being used.

If it is determined in step 2168 that there are multiple valuesavailable, the subroutine continues to step 2170 to execute the MediateAvailable Values subroutine to produce a mediated value from themultiple available values, and in step 2172 sends the produced mediatedvalue and any additional information about the value (e.g., properties,an associated uncertainty value, an indication of the server thatproduced the value, an indication of the mediator used to produce thevalue, etc.) to the requester. If it was instead determined in step 2168that there are not multiple values available, the subroutine continuesto step 2174 to determine if a single value is available, and if notcontinues to step 2178 to send an error message to the requester. If itis instead determined that there is a single value available, thesubroutine continues to step 2176 and sends the value and any additionalinformation to the requester. After steps 2154, 2172, 2176 or 2178, orif it was determined in step 2125 that there were no requests identifiedor in step 2142 that there were no more requests, the subroutinecontinues to step 2195 and returns.

FIG. 22 is a flow diagram of an embodiment of the Process ReceivedAttribute Value subroutine 2200, as illustrated in the accompanyingfigure and described elsewhere. In particular, the subroutine receivesan attribute value from a server, stores the value if appropriate (e.g.,in a cache or long-term storage), processes additional receivedinformation associated with the value if appropriate, and processes anyconditions related to the received value. The subroutine begins in step2205 where it receives an indication of a received attribute value. Thesubroutine then continues to step 2210 to determine if the attribute forwhich the value is received is registered, and if not continues to step2215 to send an error message to the server. If it is instead determinedin step 2210 that the attribute is registered, the subroutine continuesto step 2220 to determine if additional information about the value wasreceived from the server. If so, the subroutine continues to step 2225to execute the Process Additional Information About Received Valuesubroutine.

After step 2225, or if it was instead determined that additionalinformation about the value was not received from the server, thesubroutine continues to step 2230 to determine whether values for theattribute are being cached or otherwise temporarily stored. If so, thesubroutine continues to step 2235 to cache the received value as well asany additional information received. Those skilled in the art willappreciate that the length of time used for caching can vary in avariety of ways, such as based on the type of information or for aparticular attribute. After step 2235, or if it was instead determinedthat values are not being cached for the attribute, the subroutinecontinues to step 2240 to determine if values for the attribute arebeing stored in a long-term manner (e.g., being logged). If so, thesubroutine continues to step 2245 to store the received value as well asany additional information received.

After step 2245, or if it was instead determined in step 2240 thatvalues are not being stored for the attribute, the subroutine continuesto step 2250 to determine if the value and/or any additional informationabout the value triggers any active stored conditions. In step 2255, ifthere are any such conditions, the subroutine continues to step 2260 toselect the next such condition, beginning with the first. After step2260, the subroutine continues to step 2265 to send a message to theentity associated with the condition (e.g., a client that created thecondition) to indicate that the condition is satisfied. After step 2265,the subroutine continues to step 2270 to determine if the conditionshould now be removed. If so, the subroutine continues to step 2275 toremove the condition, and if not the subroutine continues to step 2280to determine if the condition should now be deactivated. If so, thesubroutine continues to step 2285 to deactivate the condition. Aftersteps 2275 or 2285, or if it was instead determined in step 2280 thatthe condition is not to be deactivated, the subroutine continues to step2290 to determine if there are more triggered conditions. If so, thesubroutine returns to step 2260 to select the next such condition. Afterstep 2215, or if it was instead determined in step 2255 that there werenot any triggered conditions or in step 2290 that there were no moretriggered conditions, the subroutine continues to step 2295 and returns.

In the illustrated embodiment, attribute values are received by thecharacterization module from servers either when the characterizationmodule requests a new value from the server or when the server pushes anew value to the characterization module. In some embodiments in which aserver has previously sent an attribute value to the characterizationmodule in response to a request, the server may later send updatedvalues for the attribute to the characterization module without a laterrequest from the characterization module, such as if a more accurate orupdated value is obtained by the server. In addition, in otherembodiments servers could provide other types of information that couldbe received and processed by the characterization module. In particular,a server could provide a variety of types of meta-information aboutattribute values to the characterization module, such as informationabout a technique used to generate a value or an indication that a newvalue is available without sending the value until requested.

FIG. 23 is a flow diagram of an embodiment of the Process AdditionalInformation About Received Value subroutine 2225, as illustrated in theaccompanying figure and described elsewhere. As illustrated anddiscussed elsewhere, a variety of types of information related toattribute values (e.g., uncertainty or accuracy information, a timestampof when the value was created or supplied or was most accurate, anindication that the value is a constant, indications of restrictions onwhether the availability of the attribute instance or of the particularvalue should be available to any or to specified CCs, data type, units,a format version, a name, any generic attribute property supplied by theCS, etc.) can be received from CSes, can be used by the CM to determinewhether and how to supply the values to CCs, can be supplied to CCs, andcan be used by CCs when processing the received attribute values. Forexample, units as indicated below could be specified.

Quantity Measured Unit Distance Meter Mass/Weight Kilogram TemperatureCentigrade Time Second Speed Meters per second Acceleration Meters persecond² Arc Radians Data size Bytes Data Throughput Bytes per secondForce Newtons Power Watts Energy Joules

In addition, uncertainty of an attribute value can be indicated in avariety of ways. An example of an uncertainty specification is asfollows. For each attribute instance there is a finite likelihood thatthe real quantity being measured is not the same as the value beingexpressed. For example, the speedometer of a car may show 30 mph whenthe “true” instantaneous speed is 32.56 mph. There are numerous factorsthat may give rise to these discrepancies, including the following:precision of measuring apparatus, conversion of continuous quantities todiscrete values in the measurement process, random fluctuations,temporal variation, systematic errors, and measurement latency. Sincedifferent measured quantities have different sources of uncertainty, itis impossible to foresee and account for each individually. It istherefore helpful to express the overall effects with a generalcharacterization of uncertainty. One type of uncertainty valuesrepresent the cumulative effects of all possible discrepancy sources.These uncertainty values may conform to a single, universal definitionso that attribute mediators and clients can make effective use of them.Thus, the following definition of uncertainty, which is based upon thedefinition of standard deviation for random fluctuations about a meanvalue, could be used for numeric values:

For an attribute instance value, μ, the associated uncertainty, σ, shallrepresent the likelihood that the following condition has a 68%probability of being true:μ_(true)−σ≦μ≦μ_(true)+σ

Where μ_(true) represents the “true” value that the attributerepresents.

As with uncertainty, a value timestamp can be indicated in a variety ofways. An example of a timestamp specification is as follows. Attributevalues may be thought of as representations of a particular quantity ata point in time. Often this time is not proximate to that of use, so itcan be useful to provide the proper timestamp along with the value. Oneversion of a timestamp is defined as follows:

The timestamp represents the moment at which the associated value wouldhave been valid had it been measured directly at that moment. Thisdefinition results in some attributes having timestamps that do notcorrespond to the time at which their values were calculated. Forinstance, an attribute that represents the acceleration of the user canbe calculated by looking at the change in velocity over a period oftime. The necessary computations may further delay the availability ofthe acceleration value. This timestamp is thus specified to representthe time at which the acceleration was “most” valid, which in this casecould be the middle of the time period during which the velocity wasmeasured.

Other types of additional information related to an attribute value caninclude history information (e.g., frequency of past use and pastpopularity information), an indication of the supplier of the attribute,indications of equivalent attributes (e.g., for mediation purposes or ifa value for this attribute is not available at a later time),indications of clients that have registered for this attribute orconsumed values for the attribute, descriptions of clients in order totrack statistics, information to be used to evaluate characterizationmodule efficiency and/or to facilitate process optimization, andindication of a verification of accuracy (e.g., from a third-party, orof the value generation technique that was used), a consumer rating orreputation based on input from other clients (e.g., efficiency orreliability), a cost to use the value (e.g., an actual price, or anamount of time needed to retrieve or process the value), futureavailability of the attribute value (e.g., how intermittent additionalvalues may be), a version of the attribute, etc.

The subroutine illustrated in FIG. 23 begins in step 2305 whereadditional information about an attribute value is received. Thesubroutine continues to step 2310 to determine if a timestamp isreceived, and if so continues to step 2315 to associate the timestampinformation with the received value. After step 2315, or if it wasinstead determined that a timestamp is not received, the subroutinecontinues to step 2320 to determine if uncertainty or other accuracyinformation is received, and if so continues to step 2325 to associatethat information with the received value. After step 2325, or if it wasinstead determined that uncertainty or other accuracy information is notreceived, the subroutine continues to step 2330 to determine if accuracydecay information (e.g., the rate at which the accuracy of the valuechanges over time) is received, and if so continues to step 2335 toassociate that information with the received value. After step 2335, orif it was instead determined that accuracy decay information is notreceived, the subroutine continues to step 2340 to determine ifinformation indicating that the value is a constant is received, and ifso continues to step 2345 to associate that information with thereceived value. After step 2345, or if it was instead determined thatconstant-related information is not received, the subroutine continuesto step 2350 to determine if information about which clients are to haveaccess to the supplied value is received, and if so continues to step2355 to associate that information with the received value so thatclient access to the attribute value is so restricted. After step 2355,or if it was instead determined that client access information is notreceived, the subroutine continues to step 2360 to associate any otherreceived additional information with the received value, and thencontinues to step 2360 and returns. Those skilled in the art willappreciate that the various types of additional information can beassociated with the received value in a variety of ways, such as byusing a data structure to represent a received value that includeselements for the various types of associated information.

FIG. 24 is a flow diagram of an embodiment of the Mediate AvailableValues subroutine 2400, as illustrated in the accompanying figure anddescribed elsewhere. As illustrated and discussed elsewhere, a varietyof different types of mediators can be defined and specified. Forexample, some mediators include the following.

Mediator Name Description First The first attribute instance that wascreated. Last The last attribute instance that was created. Fast Thefirst attribute instance to respond to a request for evaluation.Confidence The attribute instance with the lowest uncertainty. FreshnessThe attribute instance with the newest data value. Average The attributeinstances are averaged and the result returned. Vote Two or moreattributes that agree overrule ones that do not. User Choice The user ispresented with a choice of which instance to use. Fast Decay Theinstances' confidence is attenuated quickly over time based upon the ageof the data. The attenuated confidence is used to select the instance.Slow Decay The instances' confidence is attenuated slowly over timebased upon the age of the data. The attenuated confidence is used toselect the instance.Those skilled in the art will appreciate that a variety of othermediators could similarly be used, including using the previously usedvalue or a default value. In addition, other techniques could also beused, such as indicating that no value is available, asking a user tochoose between available values or to provide additional instructions,repeatedly trying to obtain an appropriate value, attempt to identifynew possible sources or a new mediation mechanism or technique, etc.

The subroutine begins at step 2405 where an indication of the valuesavailable for the mediation are received. The subroutine then continuesto step 2410 to determine if a requester of the mediated value indicateda mediator to be used, and if so continues to step 2415 to select thatmediator. If it is instead determined that the requester did notindicate a mediator to be used, the subroutine continues to step 2420 todetermine if a supplier of one or more of values being mediatedindicated a mediator to be used, and if so continues to step 2425 toselect that mediator. If it is instead determined that a supplier didnot indicate a mediator to be used, the subroutine continues to step2430 to determine if a default mediator is available, and if socontinues to step 2435 to select that mediator. If it is insteaddetermined that a default mediator is not available, the subroutinecontinues to step 2440 to determine the mediators that are available tobe used and then in step 2445 selects one of the available mediators.After steps 2415, 2425, 2435 or 2445, the subroutine continues to step2450 to apply the selected mediator to the available values in order toselect one or the available values or to generate a related value basedon the available values. The subroutine then continues to step 2455 toreturn the mediated value, and returns. Those skilled in the art willappreciate that in other embodiments mediators could be identifiedand/or obtained in other manners, such as by being specified bythird-parties that are not acting as a client, server, orcharacterization module.

FIG. 25 is a flow diagram of an embodiment of the Pull Attribute ValueFrom Server subroutine 2160, as illustrated in the accompanying figureand described elsewhere. In particular, the subroutine begins in step2505 where an indication of a request for an attribute instance value isreceived. The subroutine then continues to step 2510 to determine if anID for the request has been received. If not, the subroutine continuesto step 2515 to generate a unique request ID. After step 2515, or if itwas instead determined that an ID for the request has been received, thesubroutine continues to step 2520 to request an attribute value from theserver registered for the attribute instance, including the unique IDwith the request. The unique ID is included so that any circularreferences during the requests can be detected, as explained in greaterdetail below. The subroutine next continues to step 2525 to receive inresponse an attribute value and optionally additional information, or toinstead receive an error message. In step 2530, the received informationor error message is sent to the requester of the value, and in step 2595the subroutine returns.

FIG. 26 is a flow diagram of an embodiment of the Push Attribute ValueTo Client subroutine 2140, as illustrated in the accompanying figure anddescribed elsewhere. In particular, in the first step the subroutinereceives an indication of an attribute instance value and of a client toreceive that value. The subroutine then continues to the second step todetermine if additional information is associated with the indicatedvalue, and if so retrieves that additional information. After retrievingthe additional information, or if it was instead determined that thereis no associated additional information, the subroutine next sends thevalue and any available additional information to the indicated client.The subroutine then returns.

FIG. 27 is a flow diagram of an embodiment of the Context Client routine2700. The routine receives messages from the CM as well as instructionsfrom users, sends messages to the CM, and processes received messagesand instructions. In some embodiments, a CC could indicate to the CM aninterest in receiving values for one or more attributes, but not beginto otherwise execute (e.g., by dynamically loading code) until a valuefor one of the attributes is supplied by the CM. The routine begins instep 2702 where the CC registers with the CM. The routine then continuesto step 2704 where the CC optionally registers for one or moreattributes of interest with the CM. The routine continues to step 2706where it receives an indication of an instruction or of informationreceived. The routine continues to step 2708 where it determines whetherinformation or an instruction has been received.

If information has been received, the routine continues to step 2710 todetermine if information about the satisfaction of a notificationrequest has been received, and if so continues to step 2712 to processthe notification satisfaction information and to take appropriateaction. If notification information has not been received, the routinecontinues to step 2714 to determine if information about thesatisfaction of a condition has been received, and if so continues tostep 2716 to process the condition satisfaction information and to takeappropriate action. If condition information has not been received, theroutine continues to step 2718 to determine if a status message from theCM has been received (e.g., that a particular CS or a particularattribute has been unregistered), and if so continues to step 2720 toprocess the status information and to take appropriate action. If astatus message has not been received, the routine continues to step 2722to determine if an attribute value has been pushed to the CC. If not,the routine continues to step 2724 to process the other information thathas been received, and if so continues to step 2726 to determine ifadditional information related to the value has also been received. Ifadditional information has been received, the subroutine continues tostep 2730 to process the value and the additional information, and ifnot the routine continues to step 2728 to process the value.

If it was instead determined in step 2708 that an instruction wasreceived, the routine continues to step 2740 to determine if theinstruction is to send a notification-related request (e.g., toestablish a request) to the CM, and if so the routine continues to step2742 to send the request. If the instruction is not to send anotification-related request, the routine continues to step 2744 todetermine if the instruction is to send a condition-related request(e.g., to temporarily suspend an existing condition), and if so theroutine continues to step 2746 to send the request to the CM. If acondition-related request was not received, the routine continues tostep 2748 to determine if an instruction to send an attribute valuerequest was received, and if so continues to step 2750 to request theattribute value from the CM. In addition, other information could alsobe specified with the request, such as a mediator to be used if thereare multiple available values or an indication of a particular supplierfrom whom to receive the value. After step 2750, the routine thencontinues to step 2752 to wait for the requested value or an errormessage. If it is determined in step 2754 that a value was received, theroutine continues to step 2726, and if not the routine continues to step2756 to process the error message.

If it was instead determined in step 2748 that the instruction was notto send an attribute value request, the routine continues to step 2758to determine if the instrument was to send another type of request. Ifso, the routine continues to step 2760 to send the request, and if notthe routine continues to step 2762 to perform another instruction asindicated. A variety of other types of requests could be sent to the CM,such as to shutdown the CM or a CS, to launch a CS, to specify a defaultmediator for the CM, etc. After steps 2712, 2716, 2720, 2724, 2728,2730, 2742, 2746, 2756, 2760, or 2762, the routine continues to step2770 to determine whether to continue. If not, the routine continues tostep 2772 to unregister the registered attributes for the CC, next tostep 2774 to unregister the client with the CM, and then to step 2795 toend. If it is instead determined to continue, the routine continues tostep 2776 to determine whether any currently registered attributesshould be unregistered, and if so continues to step 2778 to unregisterthe attributes with the CM. After step 2778, or if it was determined notto unregister any attributes, the routine continues to step 2780 todetermine whether to register any additional attributes. If so, theroutine continues to step 2782 to register for one or more attributes ofinterest. After step 2782, or if it was determined not to register anyadditional attributes, the routine returns to step 2706.

FIG. 28 is a flow diagram of an embodiment of the Context Server routine2800. The routine receives messages from the CM as well as instructionsfrom users, sends messages to the CM, and processes received messagesand instructions. In some embodiments, a CS could indicate to the CM anability to supply values for one or more attributes, but not begin tootherwise execute (e.g., by dynamically loading code) until a value isrequested. The routine begins in step 2802 where the CS registers withthe CM. The routine then continues to step 2804 where it registers withthe CM for one or more attributes for which the CS has the ability tosupply values. The routine continues to step 2806 where it receives anindication of an instruction or of information received. The routinecontinues to step 2808 where it determines whether information or aninstruction has been received.

If an instruction was received, the routine continues to step 2810 todetermine if the instruction is to send a notification-related request(e.g., to establish a request) to the CM, and if so the routinecontinues to step 2812 to send the request. If the instruction is not tosend a notification-related request, the routine continues to step 2814to determine if the instruction is to send a condition-related request(e.g., to temporarily suspend an existing condition), and if so theroutine continues to step 2816 to send a request to the CM. If acondition-related request was not received, the routine continues tostep 2818 to determine if the instruction was to send another type ofrequest. If so, the routine continues to step 2820 to send the request,and if not the routine continues to step 2822 to perform anotherinstruction as indicated.

If it was instead determined in step 2808 that information has beenreceived, the routine continues to step 2830 to determine if informationabout the satisfaction of a notification request has been received, andif so continues to step 2832 to process the notification information andto take appropriate action. If notification information has not beenreceived, the routine continues to step 2834 to determine if informationabout the satisfaction of a condition has been received, and if socontinues to step 2836 to process the condition information and to takeappropriate action. If condition information has not been received, theroutine continues to step 2838 to determine if a status message from theCM has been received (e.g., that a particular CC has registered), and ifso continues to step 2840 to process the status information and to takeappropriate action.

If a status message has not been received, the routine continues to step2850 to determine if a pull attribute value request has been received bythe CS, along with an ID that uniquely identifies the request. Theunique ID in this example embodiment is used to allow the context serverto determine if a circular reference exists when determining therequested attribute value. For example, consider the situation in whichCS 1 is registered to supply values for attribute 1, and CS 2 isregistered to supply values for attribute 2. In addition, imagine thatthe calculation of the value for attribute 1 depends on the value forattribute 2. Thus, when CS 1 receives a pull request to supply the valuefor attribute 1, it requests the value for attribute 2 from the CM,which in turn request the value from CS 2. After receiving the value forattribute 2 from CS 2 via the CM, CS 1 can then calculate the value forattribute 1 and satisfy the initial request by supplying the value tothe CM. If, however, CS 2 also depends on the value for attribute 1 inorder to calculate the value for attribute 2, a circular reference mayexist. In that situation, after CS 1 requests the value of the attribute2 in order to calculate the value for attribute 1, CS 2 may in turnrequest the value of attribute 1 from CS 1 (via the CM), thus creating aloop such that neither attribute value can be calculated. In order todetect such circular references, the example routine uses a unique IDpassed along with attribute value requests. Alternate equivalent ways ofidentifying circular references could instead be used, or no suchprocessing could be performed.

In the illustrated embodiment, if it is determined that a pull attributevalue request has been received by the CS, the routine continues to step2852 to determine if the received request ID matches a temporarilystored ID for the same attribute value. If so, a circular referenceexists, and the routine continues to step 2853 to return an errormessage. If the ID does not match, the routine continues to step 2854 todetermine the input information needed (if any) to calculate therequested value. The routine then continues to step 2856 to determine ifthe value of another attribute is needed. If so, the routine in step2858 temporarily stores an indication of the attribute whose value isbeing calculated and of the ID. The routine then continues to step 2860to request the attribute value needed, including the received ID. Instep 2862, the routine waits for the requested value or error message.After receiving the value or error message, the routine continues tostep 2864 to determine if more attribute values are needed, and if so toreturn to step 2860. After all of the needed attribute values have beenreceived, the routine continues to step 2866 to remove the temporarilystored attribute value and ID, and then continues to step 2868 todetermine if any errors were received for needed attribute values suchthat sufficient information to calculate the value requested of the CSis not available. If so, the routine continues to step 2853 to signal anerror.

If there are no such errors, or if it was instead determined in step2856 that no attribute values were needed, the routine continues to step2870 to determine if any sensor values or other input information isneeded to calculate the value requested of the CS. If so, the routinecontinues in steps 2872 through 2876 to request and receive the sensoror other input information that is needed. The routine then continues tostep 2878 to determine if any errors were received for needed sensorvalues or other input information such that sufficient information tocalculate the value request of the CS is not available. If so, theroutine continues to step 2853. If no such errors occurred, or if it wasinstead determined in step 2870 that no sensor or other inputinformation was needed, the routine continues to step 2887 to calculatethe requested attribute value based on the received information. Theroutine then continues to step 2888 to optionally calculate additionalinformation about the value that characterizes it (e.g., a timestamp oruncertainty information), and then continues to step 2889 to send thevalue and any additional information to the CM to satisfy the request.

If it was instead determined in step 2850 that an attribute valuerequest was not received, the routine continues to step 2880 todetermine if sensor or other input information has been pushed to theCS. If not, the routine continues to step 2882 to process the otherinformation received, and if so continues to step 2884 to determine ifthe CS has sufficient information to calculate one or more attributevalues based on the received input information and other storedinformation. If so, the routine continues to step 2887 to calculatethose values and to push them to the CM, and if not the routinecontinues to step 2886 to store the sensor information for later use. Inalternate embodiments, the CS could request other information that isneeded to calculate an attribute value when sensor or other inputinformation is received, rather than waiting until all necessaryinformation has been received.

After steps 2812, 2816, 2820, 2822, 2832, 2836, 2840, 2853, 2882, 2886or 2889, the routine continues to step 2890 to determine whether tocontinue. If not, the routine continues to step 2891 to unregister theregistered attributes for the CS, next to step 2892 to unregister theserver with the CM, and then to step 2899 to end. If it was insteaddetermined to continue, the routine continues to step 2893 to determinewhether any currently registered attributes should be unregistered, andif so continues to step 2894 to unregister the attributes with the CM.After step 2894, or if it was determined not to unregister anyattributes, the routine continues to step 2896 to determine whether toregister any additional attributes. If so, the routine continues to step2897 to register for one or more attributes of interest. After step2897, or if it was determined not to register any additional attributes,the routine returns to step 2806.

As discussed previously, a variety of error messages can be used by theCS, CM, and CC. Example error messages include the following.

-   -   Attribute already exists—Occurs when a CS attempts to create an        attribute instance that already exists.    -   Attribute does not exist—Occurs when the CM receives a request        for an attribute that does not exist.    -   Attribute instance does not exist—Occurs when the CM receives a        request for a specific instance of an attribute which is not        registered.    -   Attribute mediator does not exist—Occurs when a request for an        attribute mediator could not be fulfilled because the name does        not correspond to an existing attribute mediator.    -   Attribute unavailable—Occurs when a CS determines that it cannot        satisfy a request for reasons other than when an attribute upon        which it depends returns an error.    -   CS already running—A request to launch a CS could not be        completed because the CS was already running.    -   CS does not exist—A request has been made for a CS that has not        registered.    -   CS not found—A request to launch a CS could not be completed        because the CS was not found.    -   CS unavailable—A request was made to a CS that cannot respond.    -   Condition already exists—Occurs when a client attempts to create        a condition with a name that is already in use.    -   Condition does not exist—A request has been made for a        non-existent condition.    -   Event already exists—Occurs when a client attempts to create an        event with a name that is already in use.    -   Event does not exist—A request has been made for a non-existent        event.    -   Inconsistent attribute data type—Occurs when a CS registers or        provides an attribute instance for an attribute that already        exists that has a different data type.    -   Request timed out—Occurs when the timeout has been exceeded and        the request cannot be satisfied.        When error messages are received in some embodiments, the module        receiving the error may make the request again but specify that        diagnostic information is to be received, thus assisting in        identifying the source of the error.

From the foregoing it will be appreciated that, although specificembodiments have been described herein for purposes of illustration,various modifications may be made without deviating from the spirit andscope of the invention. Accordingly, the invention is not limited exceptas by the appended claims. In addition, while certain aspects of theinvention are presented below in certain claim forms, the inventorscontemplate the various aspects of the invention in any available claimform. For example, while only one some aspects of the invention maycurrently be recited as being embodied in a computer-readable medium,other aspects may likewise be so embodied. Accordingly, the inventorsreserve the right to add additional claims after filing the applicationto purse such additional claim forms for other aspects of the invention.

1. A method in a computer for providing information about a currentstate that is modeled with multiple state attributes, comprising:receiving from a first source an indication of an ability to supplyvalues for an indicated one of the state attributes of the modeledcurrent state; receiving from a second source an indication of anability to supply values for another of the state attributes of themodeled current state; and after receiving an indication of theindicated attribute from a first client, determining that the firstsource is available to supply a value for the indicated attribute;obtaining from the first source an indication of the value andinformation describing the indicated value, the information describingthe value includes at least a likelihood of accuracy of the indicatedvalue; comparing the received likelihood of accuracy of the indicatedvalue with a minimum accuracy specified by the client; determining basedat least in part on the descriptive information whether the indicatedvalue is appropriate to be supplied to the client, determining includesat least verifying that the received likelihood of accuracy of theindicated value is equal to or greater than the minimum accuracy; andwhen it is determined that the indicated value is appropriate, supplyingthe indicated value to the client.
 2. The method of claim 1 wherein thedescriptive information indicates that the indicated value is a constantvalue for the indicated state attribute.
 3. The method of claim 2including: storing the obtained constant value; and supplying the storedconstant value to clients in response to fUture requests for a value ofthe indicated state attribute.
 4. The method of claim 1 wherein thedescriptive information indicates a name of the indicated attribute. 5.The method of claim 4 wherein the indicated attribute is part of apredefined taxonomy of attributes such that each of the attributes inthe predefined taxonomy has a predefined name.
 6. The method of claim 4wherein the indicated attribute is dynamically defined by the firstsource, and wherein the descriptive information provides an indicationof an applicability of the indicated value so as to assist clients indetermining whether to use the indicated value.
 7. The method of claim 1wherein the descriptive information indicates a time at which theindicated value was generated.
 8. The method of claim 7 wherein theobtaining of the value includes requesting the first source to supply avalue, the requesting including an indication of a time period, andwherein the indicated value is determined to be appropriate if the timeperiod includes the time at which the indicated value was generated. 9.The method of claim 1 wherein the descriptive information indicates atime at which the indicated value is most accurate.
 10. The method ofclaim 9 wherein the obtaining of the value includes requesting the firstsource to supply a value, the requesting including an indication of atime period, and wherein the indicated value is determined to beappropriate if the time period includes the time at which the indicatedvalue is most accurate.
 11. The method of claim 9 including: storing theindicated value; and in response to receiving requests from clients fora value of the indicated state attribute, supplying the stored value tothe clients while a difference from a current time to the time at whichthe stored value is most accurate is less than a threshold.
 12. Themethod of claim 1 wherein the descriptive information indicates aprecision of the indicated value.
 13. The method of claim 1 wherein thedescriptive information indicates properties of the indicated value. 14.The method of claim 1 wherein the descriptive information indicates agroup of at least one authorized client, and wherein the indicated valueis determined to be appropriate for the client if the client is one ofthe authorized clients.
 15. The method of claim 1 wherein thedescriptive information indicates a version of the first source.
 16. Themethod of claim 1 wherein the descriptive information indicates how theindicated value was generated.
 17. The method of claim 1 wherein thedescriptive information indicates how the indicated value is to beinterpreted.
 18. The method of claim 1 wherein the received indicationfrom the first client is a request for a value of the indicatedattribute, and wherein the obtaining of the value from the first sourceincludes requesting the first source to supply the value, the requestingin response to the receiving of the request from the first client. 19.The method of claim 1 wherein the determining of whether the indicatedvalue is appropriate includes determining whether the obtaineddescriptive information satisfies a specified criteria.
 20. Acomputer-readable storage medium whose contents cause a computing deviceto provide information about a current state that is modeled withmultiple state attributes, by: receiving from a first source anindication of an ability to supply values for an indicated one of thestate attributes of the modeled current state; receiving from a secondsource an indication of an ability to supply values for the indicatedone of the state attributes of the modeled current state; afterreceiving an indication of the indicated attribute from a first client,determining that the first source is available to supply a first valuefor the indicated attribute; obtaining from the first source anindication of the first value and information describing the indicatedfirst value; determining that the second source is available to supply asecond value for the indicated attribute; obtaining from the secondsource an indication of the second value and information describing theindicated second value; determining based at least in part on thedescriptive information and a defined mediator policy which of theindicated values is most appropriate to be supplied to the client; andwhen it is determined which of the indicated values is most appropriate,supplying the most appropriate value to the client.
 21. A computingdevice for providing information about a current state that isrepresented with multiple attributes, comprising: an attribute mappingmodule that is capable of receiving from a first source an indication ofan ability to supply values for an indicated one of the attributes ofthe current state and of receiving from a second source an indication ofan ability to supply values for the indicated one of the attributes ofthe current state; an attribute value request module that is capable ofreceiving an indication from a first client of the indicated attribute;and an attribute value supplier module that is capable of, after thereceiving of the indication from the first client, requesting the firstand second sources to each supply a value of the indicated attribute,receiving from each of the first and second sources an indication of therequested value and information describing the received value,determining based on the received descriptive information and a mediatorpolicy which one of the two received requested values is mostappropriate to be supplied to the client, and supplying the mostappropriate received value to the client when it is determined which ofthe two received requested values is most appropriate, the mediatorpolicy is selected by the first client from a set of available mediatorpolicies.